In the western interior basin, wave-dominated, deltaic deposits provide an important economic model for exploration of oil and gas and thick, laterally extensive economic coals. Recent studies in the Upper Cretaceous Mesaverde Group (Rock Springs Formation of southwestern Wyoming and Blackhawk Formation of eastern Utah) provide insight to the characteristics of wave-dominated, deltaic environments. Widespread, delta-front, sheet sandstones provide significant reservoirs for oil and gas and a platform upon which thick laterally continuous coals can develop.

Wave-dominated deltas are characterized by thick, prodelta deposits composed of graded, bedded siltstones and mudstones. Capping the prodelta deposits are distributary-mouth, bar sandstones at the mouth of distributary channels. In the interchannel areas, delta-front, sheet sandstones accumulate owing to high wave energy. They are laterally continuous along depositional strike as well as dip. Coeval, distributary channels tend

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to be straight or have a low sinuosity with sediment fills ranging from fine mudstones to coarse-grained sandstones. Delta-plain deposits consist of lagoonal, bayfill mudstones and small-splay or bayhead-delta sandstones formed in areas behind and marginal to the delta front. Numerous coarsening-upward sequences are capped by localized coals. Fluvial and upper delta-plain areas consist of channel, levee, and backswamp materials that are laterally discontinuous.

Features such as those observed in these wave-dominated delta deposits are easily recognizable on seismic lines. The seismic lines can be used to target favorable areas of hydrocarbon and coal accumulation.

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